The field of the invention relates generally to nano-fabrication of structures. More particularly, the present invention is directed to a technique to reduce defect replication in patterns formed during nano-scale fabrication.
Nano-fabrication involves the fabrication of very small structures, e.g., having features on the order of nano-meters or smaller. One area in which nano-fabrication has had a sizeable impact is in the processing of integrated circuits. As the semiconductor processing industry continues to strive for larger production yields while increasing the circuits per unit area formed on a substrate, nano-fabrication becomes increasingly important. Nano-fabrication provides greater process control while allowing increased reduction of the minimum feature dimension of the structures formed. Other areas of development in which nano-fabrication has been employed include biotechnology, optical technology, mechanical systems and the like.
An exemplary nano-fabrication technique is commonly referred to as imprint lithography. Exemplary imprint lithography processes are described in detail in numerous publications, such as United States patent application publication 2004/0065976 filed as U.S. patent application Ser. No. 10/264,960, entitled, “Method and a Mold to Arrange Features on a Substrate to Replicate Features having Minimal Dimensional Variability”; United States patent application publication 2004/0065252 filed as U.S. patent application Ser. No. 10/264,926, entitled “Method of Forming a Layer on a Substrate to Facilitate Fabrication of Metrology Standards”; and U.S. Pat. No. 6,936,194, entitled “Functional Patterning Material for Imprint Lithography Processes,” all of which are assigned to the assignee of the present invention.
The fundamental imprint lithography technique disclosed in each of the aforementioned United States patent application publications and United States patent includes formation of a relief pattern in a polymerizable layer and transferring a pattern corresponding to the relief pattern into an underlying substrate. The substrate may be positioned upon a motion stage to obtain a desired position to facilitate patterning thereof. To that end, a template is employed spaced-apart from the substrate with a formable liquid present between the template and the substrate. The liquid is solidified to form a solidified layer that has a pattern recorded therein that is conforming to a shape of the surface of the template in contact with the liquid. The template is then separated from the solidified layer such that the template and the substrate are spaced-apart. The substrate and the solidified layer are then subjected to processes to transfer, into the substrate, a relief image that corresponds to the pattern in the solidified layer.
To that end, imprint lithography may have unlimited resolution in pattern replication. However, this may result in difficulties related to defect sensitive applications such as microelectronic devices. The primary advantage of all “imaging” lithography solutions such as photolithography, EUV lithography, e-beam, etc. is that the machine system can be “de-tuned” to set a desired resolution limit. For example, in optical/EUV lithography, the resolution of the process is defined by R=(k1×λ)/NA, where k1 is a scaling factor that is less than 1 and is a function of mask complexity and resist dose settings; λ is the wavelength of light; and NA is the numerical aperture of the optical system. For EUV lithography, λ=˜13.2 nm. To that end, to print devices using EUV lithography with a desired resolution (dR) of 40 nm (with k1=0.8 based on acceptable mask and process complexity), NA needs to equal ˜0.264. As a result, any features that were placed on the mask that may result in features less than the desired resolution (40 nm) on the wafer may be inherently “filtered out”. This sets the threshold on what should be detectable as defects on the mask using a mask inspection tool to avoid the printing of defects that are less than dR=40 nm.
To that end, it may be desired to provide an improved method of patterning substrates substantially absent of defects employing imprint lithography.